Method to automatically control thread tension

ABSTRACT

The present invention relates to automatically controlling the tension of thread sewn while operating a sewing machine The system for controlling the tension of thread being used includes a wheel or other gripping mechanism that is in mechanical communication with a motor. When voltage and/or current is provided to the motor via electronic circuitry, the motor “pulls” on the thread with the desired force in a direction opposite to how the thread normally flows. The voltage and/or current delivered to the motor may be adjusted by a user. When the motor pulls on a thread to provide tension, the tension may be maintained independently of the sliding friction of the thread. As such, the tension is very accurate and repeatable, and provides for a tension that cannot be achieved with currently existing sewing machines.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/150,054, filed Apr. 20, 2015, which is hereby incorporated by reference in its entirety.

BACKGROUND OF INVENTION

Many machines have been developed and are commercially available for sewing quilts, comforters, and other similar textile goods. A key component to the quality of stitching the aforementioned goods is the tension of the thread being sewn. As a result, a critical part to every sewing machine is a tension device for controlling the thread tension.

Typically the method for adjusting thread tension involves two disks. An example of such a tension control device is shown and described in U.S. Pat. No. 6,595,150 to Yamazaki. The disks are typically placed over a threaded post and held in place by a spring and a knob that are threaded onto the post and held in place by a nut. The thread is passed between the disks, usually wrapping once around the post. When the position of the knob is adjusted, the amount of spring force exerted onto the disks may then be adjusted. This change in spring force results in a different amount of sliding friction on the thread. It is this friction that creates the tension in the thread being sewn.

Recently, other ways have been devised to remove the manual spring and knob and to replace the manual spring and knob with an “automatic” mechanism. One such automatic mechanism utilizes a pneumatic cylinder to exert the force onto the disk rather than the spring. By changing the air pressure of the pneumatic cylinder, the force on the disk changes, and thus the thread tension changes. Yet another method has been to replace the threaded post and nut with a ball screw or jack screw arrangement attached to a motor. By using the motor to turn the screw, a collar or other means may be moved to apply more or less force onto the spring, thus changing the tension.

The aforementioned existing methods all have at least one significant drawback. The above described methods rely on the sliding friction of the thread. Thread sliding friction can vary greatly depending on the thread quality and/or composition. If a thread is particularly slick, it may not be possible to deliver sufficient tension to produce quality stitching. If a thread is very coarse, too much tension may be delivered.

SUMMARY OF INVENTION

The present invention provides for a device and method for digitally controlling thread tension as thread is sewn. The device may operate by using a servo motor or other motor type to control the thread's tension. The specific method in which the device operates, as well as its various components, are described in greater detail below.

The method and device provide a number of benefits over the current state of the art described above. For example, with the improved device/method subject of this invention, thread tension may be maintained independently of various sliding frictions of the thread. As such, an accurate and repeatable tension may be generated that cannot be achieved with any other system. Moreover, digital control allows for an extremely high adjustment resolution of the thread tension. Such resolution is limited only by the resolution of the control circuitry contained within the device. For example, 32 bit resolution (2,147,483,647 possible adjustment steps) or greater resolution may be possible when the present invention is in use.

Moreover, the digital control of the present invention may allow for nearly instantaneous changes in thread tension. As a result, major changes in the thread tension during different parts of a stitch cycle may be made in order to optimize the final thread appearance in the resulting work when the sewing process is finished. Again, no existing method allows for such rapid changes in thread tension.

The present invention also may provide a much more reliable device and method than the other mechanisms described above as the other mechanisms include screws, springs, and other moving parts that may be subject to frequent mechanical error and thus often need to be repaired. Moreover, the present invention may include the added benefit of being able detect a break in thread during the sewing process.

A wheel or some other method for “gripping” the thread may be utilized when the device is in use. The thread may be wrapped around such a wheel that is designed to grip thread. Alternative embodiments for doing so may include passing thread between two rollers.

The wheel or other mechanism for gripping the thread may be attached and in mechanical communication with a motor. The motor may be of nearly any type, for example: DC, BLDC, Stepper, AC, Pneumatic, or Hydraulic, just to name a few. The preferred embodiment uses a DC servo motor.

When in use, a voltage and/or current that is proportional to the amount of tension required may be delivered to the motor via a user input device. The user input device may communicate or otherwise transmit the voltage and/or current to the motor via electronic circuitry. This causes the motor to “pull” on the thread with the desired force in the direction opposite of how the thread normally flows (e.g., toward the needle, where stitching takes place). The voltage and/or current may be adjusted by a user to obtain the desired tension. The tension may be a set value, or the tension may be continually changed during different parts of a stitch cycle.

Desired tension and other adjustments may be user-adjustable through the use of a knob, keypad, touchscreen or other user input device. The preferred embodiment uses a tablet or PC computer interface.

In the preferred embodiment, the motor may be attached to and in communication with, an encoder or other positioning device. When an encoder is attached to and in communication with the motor, the encoder allows the amount and velocity of the thread being sewn to be measured. Closed loop control schemes may be utilized to ensure that the thread tension is being adjusted at the desired force or velocity. The encoder may further allow the device to act as a thread break detection device. Greater detail about the present invention is provided in the detailed description of the invention below.

DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the accompanying drawings, which form a part of the specification and are to be read in conjunction therewith in which like reference numerals are used to indicate like or similar parts in the various views:

FIG. 1 is a top perspective view of the thread tension control system according to the teachings of the present invention;

FIG. 2 is an exploded perspective view of the thread tension control system of FIG. 1; and

FIG. 3 is a bottom perspective view of the thread tension control system of FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a top perspective view of a thread tension control system 1 for controlling the tension of thread used in the sewing process, hereinafter referred to as control system 1. Control system 1 may be placed in a number of locations on a sewing or quilting machine and secured thereto, in a manner well understood in the art. In the preferred embodiment, control system 1 is positioned and attached to the top of a quilting or sewing machine (not illustrated). Control system 1 may be attached to a sewing machine by means of a bracketing device, screw mechanism or other foreseeable fastening member.

Control system 1 includes a wheel 5, as illustrated in FIGS. 1 and 2, which may be used to grip thread that preferably is stitched during the sewing process. As will be described below, in the preferred embodiment, when a sewing machine is in use, thread is wrapped around wheel 5 in order to grip the thread. Alternative embodiments to replace wheel 5 in control system 1 for gripping thread may include passing the thread between two rollers, around a spool, or other means that would be foreseeable to those skilled in the art.

As shown in greater detail in FIG. 2, wheel 5 of control device 1 may be attached to and in mechanical communication with a motor 10. In the preferred embodiment motor 10 is a DC servo motor, but in alternative embodiments motor 10 may be of nearly any type able to perform the functions described herein. For example, in alternative embodiments, motor 10 may be Brushless DC (BLDC), Stepper, AC, Pneumatic, or Hydraulic. Also as shown in FIG. 2, wheel 5 and motor 10 are connected by a shaft 15. When motor 10 is in operation, as described below, it causes shaft 15 to rotate. When shaft 15 rotates, wheel 5 may also rotate such that a tension is applied to a thread. Other foreseeable members may be utilized as an alternative to shaft 15 to facilitate the rotation of wheel 5 such that it applies tension to the thread being sewn. In the illustrated embodiment, wheel 5 is affixed to motor 10 using a screw 20, washer 25, and nut 30 in a manner used widely in the art. Other means or members for attaching wheel 5 to motor 10 will also be appreciated by those skilled in the art.

As shown in greater detail in FIG. 2, control system 1 further includes a circuit board 45 comprising a plurality of electronic components. Circuit board 45 may be of the type commonly used in electronic applications. USB port 50 is also illustrated in FIG. 2. USB port 50 is shown in FIG. 1 when control system 1 is in its closed configuration, the configuration in which control system appears when in use. In the preferred embodiment, USB port 50 provides power to control system 1 in a manner well understood and known in the art.

Circuit board 45 may be in electronic communication with motor 10 by way of electronic circuitry 55. Electronic circuitry 55 is shown in FIG. 2 in exploded form. Electronic circuitry 55 is in electronic connection with motor 10 at one end and with circuit board 45 at its other end, as shown in FIG. 3.

Control system 1 may also include a user input device (not illustrated). The input device communicates with circuit board 45 via a Bluetooth connection, wireless connection, or other foreseeable means of receiving instructions and other communication from a user. In the preferred embodiment, the user uses a tablet or other PC computer interface in order to adjust the various controls of control system 1. In the alternative, the input device may be a knob, keypad, or touchscreen, though the aforementioned examples are exemplary only and are non-limiting.

Motor 10 is also preferably attached and in electronic communication with an encoder or other positioning device. The encoder (not illustrated) allows the amount of thread and/or thread velocity to be measured. In at least one embodiment, the encoder also allows control system 1 to act as a thread break detection device.

In operation, a user may use the user input device, for example a tablet, in order to adjust the amount of tension desired for the thread. When doing so, a voltage and/or current which is proportional to the amount of tension desired may be delivered to motor 10 by way of electronic circuitry 55. Subsequently motor 10 instructs shaft 15 to rotate wheel 5 and thus pull on the thread which wheel 5 is gripping with the input force in the direction opposite to which the thread normally flows (e.g., toward a needle, where stitching takes place). In alternative embodiments, the thread is passed between rollers or otherwise wrapped around a support, such as a post. Other foreseeable thread gripping members will be appreciated by those skilled in the art and are completed herein.

During the sewing process, when the thread is gripped by wheel 5 and tension is applied by motor 10, tension may be maintained independently of the thread's sliding friction. Such sliding frictions may vary greatly among thread type depending on characteristics such as thread material, thread quality, and thread thickness. Because the tension is not dependent of thread sliding friction, control system 1 may achieve accurate and repeatable thread tensions.

The user input device may also be used during the tension application process to adjust the voltage and/or current provided in order to obtain the desired tension. The tension provided may be a set value, or the tension may continually change during different parts of a stitching cycle. Closed loop control schemes may be utilized in order to provide the desired thread tension. The changes in thread tension that may be desired are preferably nearly instantaneous due to the electronic method utilized.

Because the thread tension is digitally controlled by a user input device in electronic communication with control system 1, high resolution and repeatable thread tensions are possible. For example, the thread tension may be adjustable to a limit that is limited only by the resolution of circuit board 45 associated with control system 1. For example, 32 bit resolution (2,147,483,647 adjustment steps) or higher is a possible maximum resolution for thread tension adjustment.

Moreover, in the preferred embodiment, the encoder may measure the amount of thread and/or thread velocity. As such, the encoder may allow control system 1 to act as a thread break detection device. For example, if the thread tension is zero, the encoder may be able to determine that the thread has broken, and that the control device 1 will shut down the sewing process until the thread is repaired and/or replaced.

From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure. It will be understood that certain features and sub combinations are of utility and may be employed without reference to other features and sub combinations. This is contemplated by and is within the scope of the claims Since many possible embodiments of the invention may be made without departing from the scope thereof, it is also to be understood that all matters herein set forth or shown in the accompanying drawings are to be interpreted as illustrative and not limiting.

The constructions described above and illustrated in the drawings are presented by way of example only and are not intended to limit the concepts and principles of the present invention. Thus, there has been shown and described several embodiments of a novel invention. As is evident from the foregoing description, certain aspects of the present invention are not limited by the particular details of the examples illustrated herein, and it is therefore contemplated that other modifications and applications, or equivalents thereof, will occur to those skilled in the art. The terms “having” and “including” and similar terms as used in the foregoing specification are used in the sense of “optional” or “may include” and not as “required”. Many changes, modifications, variations and other uses and applications of the present construction will, however, become apparent to those skilled in the art after considering the specification and the accompanying drawings. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claims which follow. 

What is claimed is:
 1. A system for automatically controlling thread tension of thread flowing toward material to be stitched, the system comprising: a wheel for gripping thread to be used during sewing; a motor for controlling the operation of the wheel; a shaft connecting the wheel to the motor such that when the motor is activated, the shaft and wheel are rotated and tension is applied to thread on the wheel in a direction opposite of the material to be stitched; and an input device in communication with the motor for applying at least one of a voltage and current which is proportional to a desired amount of tension to the motor.
 2. The system of claim 1, wherein the motor is one of a: DC servo, BLDC, Stepper, AC, Pneumatic, or Hydraulic motor.
 3. The system of claim 1, wherein the system further includes an encoder in electronic communication with the motor for measuring at least one of: the amount of thread and thread velocity.
 4. The system of claim 3, wherein the encoder acts as a thread break detection device.
 5. The system of claim 1, wherein the input device is one of a: tablet computer, personal computer, and a knob.
 6. A method for automatically controlling thread tension of thread flowing toward material to be stitched, the method comprising the steps of: providing a selection of a tension, that corresponds to at least one of a voltage and current, into an input device; transmitting at least one of said voltage and current to a motor via electronic circuitry; said motor pulling on a shaft in mechanical connection with a wheel for gripping thread, wherein said wheel is pulled by said shaft in a direction opposite of material to be stitched, the at least one of the voltage and current causing said motor to create the selected tension in the thread; and said one of a voltage and current delivered being adjustable via said input device.
 7. The method of claim 6, wherein the motor is one of a: DC servo, BLDC, Stepper, AC, Pneumatic, or Hydraulic motor.
 8. The method of claim 6, further comprising the step of measuring at least one of: the amount of thread and thread velocity via an encoder in electronic communication with the motor.
 9. The method of claim 8, wherein the encoder is also able to detect a break in thread.
 10. The method of claim 6, wherein the input device is one of a: tablet computer, personal computer, and a knob.
 11. A system for automatically controlling thread tension of thread flowing toward material to be stitched, the system comprising: a motor; a shaft attached to said motor; a wheel for gripping thread to be used during sewing also attached to said shaft, wherein when the motor is activated, the shaft and wheel are rotated and tension is applied to thread on the wheel in a direction opposite to material to be stitched; and an input device connected to the motor for applying at least one of a voltage and current which is proportional to a desired amount of tension to the motor.
 12. The system of claim 11, wherein the motor is one of a: DC servo, BLDC, Stepper, AC, Pneumatic, or Hydraulic motor.
 13. The system of claim 11, wherein the system further includes an encoder in electronic communication with the motor for measuring at least one of: the amount of thread and thread velocity.
 14. The system of claim 13, wherein the encoder acts as a thread break detection device.
 15. The system of claim 11, wherein the input device is one of a: tablet computer, personal computer, and a knob. 